CONFIGURE: Never enable release_build by default.

This changes the default for Caanoo, GP2x, GP2xWiz, OpenPandora and PS2.
For those now we only disable debug symbols and enable optimizations by
default.
COMMON: Make BufferedSeekableReadStream use the buffer with SEEK_SET and SEEK_END
SCUMM: Work around bug #3602239 ("Mac Loom crashes using opening...")

Skip music resources that don't have the "so" (song?) tag. It is
better than asserting, now that it turns out that they do exist.
SCUMM: Update handling of non so resources in Loom Mac.

This changes the warning to a debug and also updates the comment a bit.
Thanks to eriktorbjorn for checking Loom Mac in an emulator.
GUI: Allow user to display hidden files in the browser dialog.

This implements feature request #3600774 "File browser: show hidden files".
WINTERMUTE: Move Resources out of binary and into wintermute.zip
BUILD: Add wintermute.zip to resource file for Windows builds.
Merge pull request #306 from lordhoto/filechooser-hidden

GUI: Allow user to display hidden files in the browser dialog.
COMMON: Fix successive seeks in BufferedSeekableReadStream.

This fixes the failing test case added in
da8eeb9dbed2102764b3ca0697d6882bae0402cc.

Thanks to wjp for his input on this.
Merge pull request #305 from giucam/bufferedseekable

Make BufferedSeekableReadStream use the buffer with SEEK_SET and SEEK_END
SCI: Use correct priority selector in SoundCmd

It was using 'pri' instead of 'priority', apparently due to a
selector number->name translation error from 544daa5c31.

Thanks to waltervn for spotting this.
PEGASUS: Reset _lastMillis when changing rate in the timer
PEGASUS: Fix lid sequences missing a frame
CONFIGURE: Use -O3 for OpenPandora when optimizations are requested.

Formerly -O3 was only used for release builds.
WINTERMUTE: Redo the way floats are saved, break savegame compatibility with WME Lite completely.
(This also breaks compatibility with savegames from ScummVM prior to this commit, AND resets the
Savegame-version, older savegames will have differing MAGIC-numbers in their headers, and will thus
not be recognized).
WINTERMUTE: Force the screen to black after loading/saving.
WINTERMUTE: Avoid using ldepxf/frexpf
GRAPHICS: Let JPEGs pixelformat state 0 alpha bits.
WINTERMUTE: Apply color-key if no alpha-channel is present

(Instead of using the bpp to detect it).
WINTERMUTE: Avoid applying color-keys to ALL images with bpp >= 3.